How laser scanning improves fire and explosion investigations

In an explosion, it is critical to know how far pieces went and in what direction

After nearly 40 years of measuring fire and explosion scenes with a tape measure, Dr. John DeHaan, president of fire and explosion consultancy firm Fire-Ex Forensics Inc., was ready for a change. “I was pretty fed up with the whole process,” he said. “When someone came along and said that, at the push of a button, I can capture the visual image and the distance with tremendous accuracy, I said, ‘This has to be the solution.’”

For more than five years, DeHaan has been a proponent of the use of high-definition 3D laser scanning technology in this demanding field of forensics. In addition to his firm’s work in criminal and civil matters involving fires or explosions, fire deaths or injuries, and incident assessment or reconstruction, DeHaan is a prolific lecturer, instructor, scholar and author on fire- and explosion-related forensic science. “I urge its [laser scanner] adoption every time I give a presentation,” DeHaan said. “I’m the author of two major textbooks on fire and explosion investigations, and when I lecture, I show examples of laser scanning and say, ‘This is what you need to capture for your scenes.’”

The Limitations of Manual Fire- and Explosion-Incident Documentation
It’s no wonder laser scanning technology has sparked the interest of fire and explosion forensic investigation experts and agencies. Traditional manual collection of measurements in these scenes of destruction is not only laborious but also highly subject to limiting factors such as weather and scene conditions. Outdoor scenes and explosions, for example, are especially challenging. In an explosion, it is critical to know how far pieces went and in what direction. But investigators can only go so far when manually documenting such complex incidents.

“If there are only two of you,” DeHaan said, “you do the first hundred pieces or so and then say, ‘Well, never mind. We have the debris distribution field from these.’” This means that even the best investigators are bound to have omissions. “I don’t think I’ve ever done a fire scene where I remembered to take all of the dimensions that I really needed,” DeHaan said. “And you get back to the office and go, ‘Oh nuts, I didn’t measure that door. I didn’t get the ceiling height in that room.’”

The Benefits of Laser Scanning Fire and Explosion Scenes
What is beyond the scope of human capability is intrinsic to high-definition 3D laser scanning technology. Even in complex fire and explosion scenes, the laser scanner easily captures details and spatial relationships with speed, comprehensiveness and 0.25 inch accuracy, regardless of conditions and range. “That’s a huge advantage. You have this stuff captured—not only the visual image but the dimensions,” DeHaan said. “You can correct your oversights.”

Laser scanner technology enables investigators to correct oversights not only in the field but also in their analysis. With 3D point cloud processing software, millions of data points are transformed into a usable 3D virtual model of the scene exactly as it was at the time of capture. Unlike hand-drawn diagrams, laser scan data enables investigators to thoroughly explore and analyze the scene, even after the physical scene has been demolished. New computer programs can even integrate the scan data directly into fire models for analysis and hypothesis testing. “When you have it on the scan, you can call it up and say, ‘Oh look at that. I didn’t even think about that.’ So your work can be much more reliable and more easily defensible.”

Comprehensive Scene Documentation With Laser Scanning
As the understanding of fire- and explosion-related forensic science evolves—e.g., the affect of ventilation upon fire patterns—the documentation requirements also increase. “The technology needs in fire investigation itself have ramped up because investigators need to document the size of rooms, the size of window and door openings, and things like that,” DeHaan said. “And trying to get investigators to do all that with a tape measure is really tough.”

The speed, accuracy, comprehensiveness and permanence of laser scanning technology erase the pen-and-paper limitations of traditional manual documentation and analysis methods in fire and explosion incidents. “To be able to capture everything—whether you think it’s important at the moment of the investigation or not—with a laser scan,” DeHaan said, “puts it a world above any other manual methods.”

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